A supermassive black hole residing within the Large Magellanic Cloud (LMC) – a satellite galaxy – is on a collision course with the Milky Way, a recent study revealed. The LMC’s supermassive black hole is believed to be the closest of its kind outside our galaxy, located approximately 160,000 light-years away and one of the nearest galactic neighbours to our own.

To make this discovery, researchers traced the paths of 21 stars on the outskirts of the Milky Way using data from the European Space Agency’s Gaia mission – a satellite that has tracked more than a billion stars throughout the Milky Way with incredible accuracy. “It is astounding to realise that we have another supermassive black hole just down the block, cosmically speaking,” said Jesse Han from the Center for Astrophysics, Harvard & Smithsonian (CfA), who led the study. “Black holes are so stealthy that this one has been practically under our noses this whole time.”

This hidden black hole, estimated to be around 600,000 times the mass of The Sun, was detected by analysing the trajectories of hypervelocity stars – stars travelling much faster than average.

The LMC is destined to collide with our galaxy in approximately 2.4 billion years. When this collision occurs, the supermassive black hole in the LMC will migrate to the galactic centre and eventually merge with Sagittarius A* – the Milky Way’s central supermassive black hole. Astronomers believe that this is one way black holes grow from smaller sizes to even bigger ones.

It was in 1971 that British astronomers predicted the existence of a black hole at the centre of our galaxy, which was discovered three years later. Then, in 2019, the first image of a supermassive black hole was captured. Today, they are a fundamental part of our understanding of how galaxies form and evolve.

With a declination of about -70°, the LMC is visible as a faint “cloud” from the Southern Hemisphere of the Earth and from as far north as 20° N. It straddles the constellations Dorado and Mensa and has an apparent length of about 10° to the naked eye – 20 times the Moon’s diameter, from dark sites away from light pollution.

Like many irregular galaxies – those that do not have a distinct regular shape like the Milky Way’s spiral – the LMC is rich in gas and dust and is currently undergoing vigorous star formation activity. Surveys of the galaxy have found roughly 60 globular clusters, 400 planetary nebulae and 700 open clusters, along with hundreds of thousands of giant and supergiant stars.

This comes as scientists saw inside a dying star during its explosive death for the first time earlier this year, offering an unprecedented glimpse into how stars evolve. Stars can survive for millions to trillions of years before exhausting their fuel supply, with the largest ending their lives dramatically in a blast, known as a supernova.